The present invention relates to an edible spread having a continuous fat phase and to a process for the preparation thereof.
Examples of an edible spread are butter and margarine. Such products contain a discontinuous aqueous phase in an amount usually of about 15-20% by weight. Similar spreads, but containing a higher amount of discontinuous aqueous phase, for example of 60% by weight or even more, are commonly referred to as for example low calorie spread or low fat spread.
It becomes increasingly difficult to prepare a high quality product as the amount of discontinuous aqueous phase to be included is higher.
As the water content increases it becomes more difficult to obtain the required physical stability. To prevent coalescence of dispersed water droplets from occurring and obtain a stable product, GB No. 1,094,268 suggests incorporation of a thickening agent in the aqueous phase and an emulsifier in the fat phase.
The high water content, however, gives rise not only to a physical stability problem, but also tends to make the product taste watery. For this reason, and, inter alia, to improve the flavor release, milk proteins are often included. However, the presence of milk protein makes it more difficult to obtain a plastic dispersion that is both physically and microbiologically stable. Often a hydrocolloid is included to improve the physical stability. To prevent microbiological deterioration it has been suggested to include preservatives and to lower the pH. However, high concentrations of preservatives are often disliked by consumers, and high amounts of acid can adversely affect the taste of the product.
GB No. 1,450,269 is concerned with low calorie spreads, in particular spreads of which the fat portion comprises a substantial amount of butterfat. It is advised to include in the aqueous phase, milk protein and hydrocolloid. The patent discloses that for microbiological stability reasons, the pH of the aqueous phase should be less than 6.0, but on the other hand, for organoleptic reasons should not be below 4.5, preferably not below 4.8. The specification advises, in order to physically stabilize the low fat spread to employ hydrocolloid that can keep proteins soluble; mixtures of pectin and carrageenan are preferred. To obtain a stable product, partial glycerides must be included as emulsifier.
GB No. 1,450,269 discloses a process for preparing a low fat spread wherein butter is heated to 80.degree. C., cooled to 35.degree. C. and mixed with an aqueous composition containing milk protein, hydrocolloid, salt and partial glycerides at 35.degree. C. The pH is adjusted to, for instance, 5.15-5.3 and the admixture is passed through a series of scraped surface heat exchangers of the Votator A-unit type.
U.S. Pat. No. 4,103,037 also addresses the problem that the high water content of reduced fat spreads adversely affects organoleptic properties and/or the stability of such products, compared with butter or margarine and that the incorporation of protein in such products causes destabilization, both physically and microbiologically. According to the specification, gelling agent having a slip melting point of 25.degree.-35.degree. C., e.g. gelatin or Danish agar, and non-gelling protein, e.g. milk protein, should be included in the aqueous phase composition in a specified ratio, under conditions such that formation of undissolved protein particles of a major dimension of more than 5 microns is avoided. It is advised to include, as emulsifier, monoglycerides and, for bacteriological reasons, to adjust the pH to, preferably, 4.6-5.8. To prevent the protein from flocculating which, it is said, may easily occur at the lower pH values, it is advised to first prepare separate solutions of gelling agent and protein, the solution of gelling agent being substantially protein-free and having a pH of 1-7, and the solution of protein being substantially neutral, including in the protein solution a deflocculation agent, e.g. xanthan gum, locust bean gum or sodium CMC, then combining the solution of gelling agent and the substantially neutral proteinaceous solution containing the deflocculation agent, and subsequently adjusting the pH to the desired value.
U.S. Pat. No. 4,389,426 discloses that the organoleptic properties of low-fat spreads are often poor, owing to the high water content, and that often proteins are incorporated in the aqueous phase to improve this. To counteract the destabilizing effect of milk protein, gelling agents are incorporated in the aqueous phase. The mechanism of the counteraction is assumed to involve encapsulating or complexing of the protein with the gelling agent, binding of the water of the aqueous phase and increasing its viscosity.
The specification advocates to use as gelling agent, instead of the expensive gelatine, a combination of a colloid that forms a linear gel structure and a colloid capable of forming a spherical gel structure. For bacteriological reasons it is recommended that the pH should preferably be in the range from 4.6 to 5.8.
EP No. 0,011,891 mentions that it has been suggested to thicken the dispersed aqueous phase of spreads with, for example, fats, thickening agents like gums or proteins, and that in such products, frequently problems of diminished organoleptic qualities, insufficient microbiological keeping qualities and/or insufficient emulsion stability were observed. The specification teaches that in particular low fat spreads, which, it is said, frequently have too watery a taste, can be improved by incorporating in the continuous plastic fat phase a discontinuous aqueous phase consisting of non-gelled, liquid, finely dispersed droplets having a size range from 1 to 5 microns and a further discontinuous aqueous phase consisting of coarse, gelled droplets having a diameter in the range from 10 to 20 microns. Either or both of the discontinuous aqueous phases may comprise protein, in particular milk protein. It is advised to include emulsifier, e.g. phosphatides and/or partial glycerides.
The products obtained according to the above mentioned patents are not optimal. They present various compromises between the desired properties regarding physical stability, organoleptic characteristics and microbiological keepability. Compared with butter or premium margarine, the quality of the low fat spreads tends to be lower with respect to at least one of these properties, and usually with respect to two or three of them.
U.S. Pat. No. 4,520,037 aims to improve the microbiological stability of low fat spreads. The proposed product is a fat-continuous emulsion which comprises at least two distinct discontinuous aqueous phases each of which should comprise a microbiologically labile nutrient such as milk protein, vegetable protein, glucose, lactose or partially hydrolyzed starch. Furthermore, an effective amount of one or more ingredients that inhibit bacterial growth, e.g. acids, salts or preservatives, should be concentrated in each of the two aqueous phases. The product may contain more than two distinct dispersed aqueous phases, which additional aqueous phases may also contain nutrients. Any nutrients present, however, should be protected, either by an bacterial growth inhibiting ingredient as described above or by ensuring that the size of the aqueous phase droplets that contain the nutrient is less than 5 microns or even less than 2 microns.
In order to be able to prepare a stable product and to prevent intermingling and coalescence of the differently formulated aqueous phase drops from occurring, it is advised to include an emulsifier. A strong preference is expressed for emulsifiers of the polyglycerol fatty acid ester type.
A number of documents ha been published that describe the preparation of spreads using butter as starting material.
U.S. Pat. No. 4,555,411 aims to facilitate the preparation of fat-continuous low fat spreads. It teaches how to prepare such spreads by forming an emulsion and shearing and cooling it, using apparatus that is coated with or produced from hydrophobic material. The use of for example votator equipment coated with hydrophobic material causes phase inversion of for example dairy cream to occur more easily. Thus, according to the specification, low calorie butter can be prepared by phase inverting dairy cream without having to use non-dairy emulsifiers.
It is described how such a product can be prepared from a composition of melted butter, mixed with inter alia gelatin and skim milk. The water-continuous emulsion is turned into a fat-continuous low calorie butter by rapid cooling and inverting the cream by means of an A-unit and a crystallizer unit in which very high shear is applied, both of which units have been provided with a hydrophobic coating by filling them, beforehand, with fat.
U.S. Pat. No. 1,024,009, for example, describes a butter substitute made by combining milk, gelatin and butter and by emulsifying the mixture to obtain a homogeneous plastic mass. The gelatin is stated to be an emulsifying agent, and is used at a level of one heaping teaspoonful in one pint of whole milk. After combining the ingredients, the mixture is heated to melt the butter, and the mixture then cooled with agitation.
In addition, for many years the Knox Gelatin Company has distributed a recipe book which includes a recipe for stretching butter in which plain unflavored gelatin is softened in cold water, dissolved thoroughly over hot water, mixed with either fresh or evaporated milk, and the solution then whipped into softened but unmelted butter with an electric mixer until a stable mixture is formed. The mixture is then placed in a refrigerator until firm.
UK Patent Application GB No. 2,021,140 A published Nov. 28, 1979 describes a dairy blend comprising a homogeneous mixture of butter and a vegetable oil and having mixed therewith an aqueous gelatin solution. The product is made by softening butter to a temperature of 30.degree. C. to 35.degree. C. without over-softening, mixing with the softened butter a partially gelled solution of gelatin and emulsifying agent, allowing the mixture to stand, and thereafter adding the vegetable oil with continuous mixing. The solution of gelatin and emulsifier may further contain milk protein and, for example, salt. Without the addition of the vegetable oil, the product is said not to be spreadable straight out of the refrigerator.
The reduced fat spreads prepared according to these procedures using butter as starting material have distinct disadvantages. In particular, the storage properties are unsatisfactory. For example, the product made following the Knox Gelatin recipe will keep only about a week in a refrigerator.